The present invention relates to electric irons which comprise a sole plate heated by means of an electric heating resistance and a system of thermal regulation, in which a control member indicates the reference value of the temperature corresponding to the fabric to be ironed, a detector gives the image of the temperature of the sole plate, and a control system controls the opening or the closing, as a function of the difference between the reference temperature and the measured temperature, of the supply circuit of the electric heating resistance.
In certain known electric irons of this type, there is provided a safety system detecting the position of the iron, on the heel or on the sole plate, and cutting the supply of the heating resistance when the iron is left in a vertical position on the heel during a period greater than a certain limit.
Such a system is adapted to avoid accidental burning of the user or his surroundings, when the iron is unused and left on. It also permits avoiding the apparatus being subjected to prolonged and useless heating cycles, when the latter is accidentally left on.
Such a system nevertheless has the drawback of using a physical position detector, which increases the cost of the apparatus, increases its size and has decreased reliability with time and the cycles of use.
The invention proposes overcoming these drawbacks and providing an iron of the type described above, provided with a safety system without a position detector, capable of detecting reliably the stoppage of use of the apparatus.
According to the invention, the iron comprises a safety system having an electronic module which:
a) receives from the control system the information as to closure of the supply circuit of the electric heating resistance,
b) produces over a fixed time interval the sum of the durations of supply,
c) and opens the supply circuit of the electric heating resistance if the value thus obtained is below a predetermined threshold value.
Thus the system detects a magnitude represented by the quantity of heat delivered by the apparatus, characteristic of contact of the sole with a cloth or with ambient air.
According to an advantageous characteristic of the invention, the electronic module comprises a switch mounted in series with the electric heating resistance, which is actuated in response to a signal delivered by a first counter.
On the other hand, the first counter comprises a programmable integrated circuit, which has at least one supply path, a reception path for a zero set signal, an outlet path, a means for the generation of an activated clock frequency upon turning on the iron.
Moreover, the first counter delivers an opening signal to a relay whose contacts form the switch, when it has carried out an operation of counting of a time lag greater than predetermined time T1, without receiving the zero set signal, T1 being greater than T2.
Preferably, the first counter delivers simultaneously an opening signal to a relay whose contacts form the switch and a lockage signal for the means for generating associated clock frequency to the first counter, after it has carried out a counting operation of a duration greater than a predetermined time T1, without receiving a zero set signal, T1 being greater than T2.
According to another characteristic of the invention, the safety system comprises rearming means that can be actuated by the user, so as to close the relay and reactivate the means for generating clock frequency associated with the first counter, when the iron is on.
The rearming means, when actuated by the user, emit a zero set signal simultaneously to the first and second counter.
According to another embodiment, the safety system comprises an electronic module which:
a) receives from the control system information as to the closure of the supply circuit of the electric heating resistance,
b) counts over a fixed time interval the number of alternations between open and closed conditions of the supply circuit of the electric heating resistance, and opens the supply circuit of the electric heating resistance if the number thus obtained is below a predetermined threshold value.
This other embodiment permits, again by observation of the operation of the heating resistance, determining whether the latter is frequently urged to compensate the heat losses of the sole plate, and to cut the supply in the contrary case, which is taken to be characteristic of a nonuse condition.